The invention relates to an optical system for forming an image of the retina of an eye to be examined.
In order to form an image of the retina, it is already known to use contact lenses. The known systems have the disadvantage that they can form an image of only small areas of the retina, and that in order to examine the entire area of the retina, it is necessary to swing the optical system to form successive images of different regions of the retina, one after the other.
An object of the present invention is to provide an optical system which is able, from a single fixed position, to form an image of a relatively large area of the retina, approximately up to the "ora serrata."
This object is attained according to the invention by providing two lens groups which cooperate to form an image of a relatively large area of the retina. The first lens group is in substantial contact with the cornea of the eye of the patient, via the natural eye liquid or a physiological saline solution. The second lens group is spaced from the first lens group by an air space. The curvatures and refractive powers of the lenses are preferably so dimensioned that the image of the retina which is produced is flattened.
The second lens group can advantageously consist of Fresnel lenses. However, it is also possible to construct the second lens group from a combination of spherical or aspherical lenses with Fresnel lenses.
In one embodiment of the invention, an adapter for the attachment of reproduction apparatus (a camera or the like) or projection apparatus, is provided behind the second lens group.
The illumination of the fundus or retina can be effected in known manner with mono-light-transmitting fibers arranged in a ring around the imaging system. However, it is also possible to provide the first lens group with a central borehole which receives the end of a light pipe for illuminating the eye of the patient. Light is furnished to the opposite end of the light pipe from any convenient conventional illuminating means.
The advantages obtained with this invention include, in particular, the fact that the examining apparatus need not be swung or shifted from one position to another, in order to cover the entire retina. It provides an approximately 1.5 times enlargement of the fundus or retina which is being observed. In order to increase the enlargement of the image of the fundus, an ocular or a viewing lens system with documentation possibilities (e.g., a camera or other means for taking a picture) can be arranged in known manner behind the optical system.